U.S. patent number 7,875,563 [Application Number 11/729,258] was granted by the patent office on 2011-01-25 for method to create an environmentally resistant soft armor composite.
This patent grant is currently assigned to Honeywell International Inc.. Invention is credited to Henry G. Ardiff, Brian D. Arvidson, Ashok Bhatnagar, Ralf Klein, Lori L. Wagner.
United States Patent |
7,875,563 |
Ardiff , et al. |
January 25, 2011 |
Method to create an environmentally resistant soft armor
composite
Abstract
Fibrous substrates and articles that retain their superior
ballistic resistance performance after exposure to liquids such as
sea water and organic solvents, such as gasoline and other
petroleum-based products. The fibrous substrates are coated with a
multilayer polymeric coating including at least two different
polymer layers wherein at least one of the layers is formed from a
fluorine-containing polymer.
Inventors: |
Ardiff; Henry G. (Chesterfield,
VA), Klein; Ralf (Midlothian, VA), Arvidson; Brian D.
(Chester, VA), Bhatnagar; Ashok (Richmond, VA), Wagner;
Lori L. (Richmond, VA) |
Assignee: |
Honeywell International Inc.
(Morristown, NJ)
|
Family
ID: |
39794897 |
Appl.
No.: |
11/729,258 |
Filed: |
March 28, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080241494 A1 |
Oct 2, 2008 |
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Current U.S.
Class: |
442/134; 442/135;
2/2.5 |
Current CPC
Class: |
D06N
3/183 (20130101); F41H 5/0478 (20130101); Y10T
442/2623 (20150401); Y10T 442/2615 (20150401) |
Current International
Class: |
B32B
27/04 (20060101) |
Field of
Search: |
;442/65,66,134,135
;428/911 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0196695 |
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Dec 2001 |
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WO |
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0214408 |
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Feb 2002 |
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WO |
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2006132852 |
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Dec 2006 |
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WO |
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Primary Examiner: Singh-Pandey; Arti
Attorney, Agent or Firm: Wilson; Erika S.
Claims
What is claimed is:
1. A ballistic resistant fibrous composite comprising at least one
fibrous substrate having a multilayer coating thereon, wherein said
fibrous substrate comprises one or more fibers having a tenacity of
about 7 g/denier or more and a tensile modulus of about 150
g/denier or more; said multilayer coating comprising a first
polymer layer on a surface of said one or more fibers, said first
polymer layer comprising a first polymer, and a second polymer
layer on said first polymer layer, said second polymer layer
comprising a second polymer, wherein the first polymer and the
second polymer are different, and wherein at least the first
polymer comprises fluorine.
2. The ballistic resistant fibrous composite of claim 1 wherein the
first polymer comprises fluorine and the second polymer is
substantially absent of fluorine.
3. The ballistic resistant fibrous composite of claim 1 wherein the
first polymer comprises fluorine and the second polymer comprises
fluorine.
4. The ballistic resistant fibrous composite of claim 1 wherein at
least one of the first polymer and the second polymer comprises a
polychlorotrifluoroethylene homopolymer, a chlorotrifluoroethylene
copolymer, an ethylene-chlorotrifluoroethylene copolymer, an
ethylene-tetrafluoroethylene copolymer, a fluorinated
ethylene-propylene copolymer, perfluoroalkoxyethylene,
polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene
fluoride, fluorocarbon-modified polyethers, fluorocarbon-modified
polyesters, fluorocarbon-modified polyanions, fluorocarbon-modified
polyacrylic acid, fluorocarbon- modified polyacrylates,
fluorocarbon-modified polyurethanes, or copolymers or blends
thereof.
5. The ballistic resistant fibrous composite of claim 1 wherein the
second polymer comprises a polyurethane polymer, a polyether
polymer, a polyester polymer, a polycarbonate resin, a polyacetal
polymer, a polyamide polymer, a polybutylene polymer, an
ethylene-vinyl acetate copolymer, an ethylene-vinyl alcohol
copolymer, an ionomer, a styrene-isoprene copolymer, a
styrene-butadiene copolymer, a styrene-ethylene /butylene
copolymer, a styrene-ethylene/propylene copolymer, a polymethyl
pentene polymer, a hydrogenated styrene-ethylene/butylene
copolymer, a maleic anhydride functionalized
styrene-ethylene/butylene copolymer, a carboxylic acid
functionalized styrene-ethylene/butylene copolymer, an
acrylonitrile polymer, an acrylonitrile butadiene styrene
copolymer, a polypropylene polymer, a polypropylene copolymer, an
epoxy resin, a novolac resin, a phenolic resin, a vinyl ester
resin, a silicone resin, a nitrile rubber polymer, a natural rubber
polymer, a cellulose acetate butyrate polymer, a polyvinyl butyral
polymer, an acrylic polymer, an acrylic copolymer, an acrylic
copolymer incorporating non-acrylic monomers or combinations
thereof.
6. The ballistic resistant fibrous composite of claim 1 wherein
said fibrous substrate comprises one or more polyolefin fibers,
aramid fibers, polybenzazole fibers, polyvinyl alcohol fibers,
polyamide fibers, polyethylene terephthalate fibers, polyethylene
naphthalate fibers, polyacrylonitrile fibers, liquid crystal
copolyester fibers, glass fibers, carbon fibers, rigid rod fibers
comprising pyridobisimidazole-2,6-diyl (2,5-dihydroxy
-p-phenylene),or a combination thereof.
7. The ballistic resistant fibrous composite of claim 1 which
comprises a plurality of fibers in the form of a ballistic
resistant fabric.
8. A ballistic resistant article formed from the ballistic
resistant fabric of claim 7.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ballistic resistant articles having
excellent resistance to deterioration due to liquid exposure. More
particularly, the invention pertains to ballistic resistant fabrics
and articles that retain their superior ballistic resistance
performance after exposure to liquids such as sea water and organic
solvents, such as gasoline and other petroleum-based products.
2. Description of the Related Art
Ballistic resistant articles containing high strength fibers that
have excellent properties against projectiles are well known.
Articles such as bullet resistant vests, helmets, vehicle panels
and structural members of military equipment are typically made
from fabrics comprising high strength fibers. High strength fibers
conventionally used include polyethylene fibers, aramid fibers such
as poly(phenylenediamine terephthalamide), graphite fibers, nylon
fibers, glass fibers and the like. For many applications, such as
vests or parts of vests, the fibers may be used in a woven or
knitted fabric. For other applications, the fibers may be
encapsulated or embedded in a polymeric matrix material to form
woven or non-woven rigid or flexible fabrics.
Various ballistic resistant constructions are known that are useful
for the formation of hard or soft armor articles such as helmets,
panels and vests. For example, U.S. Pat. Nos. 4,403,012, 4,457,985,
4,613,535, 4,623,574, 4,650,710, 4,737,402, 4,748,064, 5,552,208,
5,587,230, 6,642,159, 6,841,492, 6,846,758, all of which are
incorporated herein by reference, describe ballistic resistant
composites which include high strength fibers made from materials
such as extended chain ultra-high molecular weight polyethylene.
These composites display varying degrees of resistance to
penetration by high speed impact from projectiles such as bullets,
shells, shrapnel and the like.
For example, U.S. Pat. Nos. 4,623,574 and 4,748,064 disclose simple
composite structures comprising high strength fibers embedded in an
elastomeric matrix. U.S. Pat. No. 4,650,710 discloses a flexible
article of manufacture comprising a plurality of flexible layers
comprised of high strength, extended chain polyolefin (ECP) fibers.
The fibers of the network are coated with a low modulus elastomeric
material. U.S. Pat. Nos. 5,552,208 and 5,587,230 disclose an
article and method for making an article comprising at least one
network of high strength fibers and a matrix composition that
includes a vinyl ester and diallyl phthalate. U.S. Pat. No.
6,642,159 discloses an impact resistant rigid composite having a
plurality of fibrous layers which comprise a network of filaments
disposed in a matrix, with elastomeric layers there between. The
composite is bonded to a hard plate to increase protection against
armor piercing projectiles.
Hard or rigid body armor provides good ballistic resistance, but
can be very stiff and bulky. Accordingly, body armor garments, such
as ballistic resistant vests, are preferably formed from flexible
or soft armor materials. However, while such flexible or soft
materials exhibit excellent ballistic resistance properties, they
also generally exhibit poor resistance to liquids, including fresh
water, seawater and organic solvents, such as petroleum, gasoline,
gun lube and other solvents derived from petroleum. This is
problematic because the ballistic resistance performance of such
materials is generally known to deteriorate when exposed to or
submerged in liquids. Further, while it has been known to apply a
protective film to a fabric surface to enhance fabric durability
and abrasion resistance, as well as water or chemical resistance,
these films add weight to the fabric. Accordingly, it would be
desirable in the art to provide soft, flexible ballistic resistant
materials that perform at acceptable ballistic resistance standards
after being contacted with or submerged in a variety of liquids,
and also have superior durability without the use of a protective
surface film in addition to a binder polymer coating.
Few conventional binder materials, commonly referred to in the art
as polymeric "matrix" materials, are capable of providing all the
desired properties discussed herein. Fluorine-containing polymers
are desirable in other arts due to their resistance to dissolution,
penetration and/or transpiration by sea water and resistance to
dissolution, penetration and/or transpiration by one or more
organic solvents, such as diesel gasoline, non-diesel gasoline, gun
lube, petroleum and organic solvents derived from petroleum. In the
art of ballistic resistant materials, it has been discovered that
fluorine-containing coatings advantageously contribute to the
retention of the ballistic resistance properties of a ballistic
resistant fabric after prolonged exposure to potentially harmful
liquids, eliminating the need for a protective surface film to
achieve such benefits. More particularly, it has been found that
excellent ballistic and environmental properties are achieved when
coating ballistic resistant fibrous materials with both a layer of
a conventional polymeric matrix material and a layer of a
fluorine-containing polymer.
Accordingly, the present invention provides a ballistic resistant
fabric which is formed with multiple layers of polymeric binder
materials. At least one of the layers comprises a
fluorine-containing polymer that offers the desired protection from
liquids, as well as heat and cold resistance, and resistance to
abrasion and wear, while maintaining good flexibility and superior
ballistic resistance properties. The polymer layers are preferably
contacted with each other as liquids to facilitate their
miscibility and adhesion at their contact interfaces.
SUMMARY OF THE INVENTION
The invention provides a fibrous composite comprising at least one
fibrous substrate having a multilayer coating thereon, wherein said
fibrous substrate comprises one or more fibers having a tenacity of
about 7 g/denier or more and a tensile modulus of about 150
g/denier or more; said multilayer coating comprising a first
polymer layer on a surface of said one or more fibers, said first
polymer layer comprising a first polymer, and a second polymer
layer on said first polymer layer, said second polymer layer
comprising a second polymer, wherein the first polymer and the
second polymer are different, and wherein at least one of the first
polymer and the second polymer comprises fluorine.
The invention also provides a method of forming a fibrous composite
comprising: a) providing at least one fibrous substrate having a
surface; wherein said at least one fibrous substrate comprises one
or more fibers having a tenacity of about 7 g/denier or more and a
tensile modulus of about 150 g/denier or more; b) applying a first
polymer layer onto the surface of the at least one fibrous
substrate, said first polymer layer comprising a first polymer; c)
thereafter, applying a second polymer layer onto the first polymer
layer, said second polymer layer comprising a second polymer; and
wherein the first polymer and the second polymer are different; and
wherein at least one of the first polymer and the second polymer
comprises fluorine.
Also provided are articles formed from the fibrous composites of
the invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic representation illustrating a process for
applying a multilayer coating onto a fibrous substrate utilizing a
hybrid coating technique.
DETAILED DESCRIPTION OF THE INVENTION
The invention presents fibrous composites and articles that retain
superior ballistic penetration resistance after exposure to water,
particularly sea water, and organic solvents, particularly solvents
derived from petroleum such as gasoline. Particularly, the
invention provides fibrous composites formed by applying a
multilayer coating onto at least one fibrous substrate. A fibrous
substrate is considered to be a single fiber in most embodiments,
but may alternately be considered a fabric when a plurality of
fibers are united as a monolithic structure prior to application of
the multilayer coating, such as with a woven fabric that comprises
a plurality of woven fibers. The method of the invention may also
be conducted on a plurality of fibers that are arranged as a fiber
web or other arrangement, which are not technically considered to
be a fabric at the time of coating, and is described herein as
coating on a plurality of fibrous substrates. The invention also
provides fabrics formed from a plurality of coated fibers and
articles formed from said fabrics.
The fibrous substrates of the invention are coated with a
multilayer coating that comprises at least two different polymer
layers, wherein at least one of the layers is formed from a
fluorine-containing polymer. As used herein, a
"fluorine-containing" polymeric binder describes a material formed
from at least one polymer that includes fluorine atoms. Such
include fluoropolymers and/or fluorocarbon-containing materials,
i.e. fluorocarbon resins. A "fluorocarbon resin" generally refers
to polymers including fluorocarbon groups.
The multilayer coatings comprise a first polymer layer on a surface
of the fibers, said first polymer layer comprising a first polymer,
and a second polymer layer on the first polymer layer, said second
polymer layer comprising a second polymer, wherein the first
polymer and the second polymer are different and wherein at least
one of the first polymer and the second polymer comprises a
fluorine-containing polymer.
For the purposes of the invention, articles that have superior
ballistic penetration resistance describe those which exhibit
excellent properties against high speed projectiles. The articles
also exhibit excellent resistance properties against fragment
penetration, such as shrapnel. For the purposes of the present
invention, a "fiber" is an elongate body the length dimension of
which is much greater than the transverse dimensions of width and
thickness. The cross-sections of fibers for use in this invention
may vary widely. They may be circular, flat or oblong in
cross-section. Accordingly, the term fiber includes filaments,
ribbons, strips and the like having regular or irregular
cross-section. They may also be of irregular or regular multi-lobal
cross-section having one or more regular or irregular lobes
projecting from the linear or longitudinal axis of the fibers. It
is preferred that the fibers are single lobed and have a
substantially circular cross-section.
As stated above, the multilayer coatings may be applied onto a
single polymeric fiber or a plurality of polymeric fibers. A
plurality of fibers may be present in the form of a fiber web, a
woven fabric, a non-woven fabric or a yarn, where a yarn is defined
herein as a strand consisting of multiple fibers and where a fabric
comprises a plurality of united fibers. In embodiments including a
plurality of fibers, the multilayer coatings may be applied either
before the fibers are arranged into a fabric or yarn, or after the
fibers are arranged into a fabric or yarn.
The fibers of the invention may comprise any polymeric fiber type.
Most preferably, the fibers comprise high strength, high tensile
modulus fibers which are useful for the formation of ballistic
resistant materials and articles. As used herein, a "high-strength,
high tensile modulus fiber" is one which has a preferred tenacity
of at least about 7 g/denier or more, a preferred tensile modulus
of at least about 150 g/denier or more, and preferably an
energy-to-break of at least about 8 J/g or more, each both as
measured by ASTM D2256. As used herein, the term "denier" refers to
the unit of linear density, equal to the mass in grams per 9000
meters of fiber or yarn. As used herein, the term "tenacity" refers
to the tensile stress expressed as force (grams) per unit linear
density (denier) of an unstressed specimen. The "initial modulus"
of a fiber is the property of a material representative of its
resistance to deformation. The term "tensile modulus" refers to the
ratio of the change in tenacity, expressed in grams-force per
denier (g/d) to the change in strain, expressed as a fraction of
the original fiber length (in/in).
The polymers forming the fibers are preferably high-strength, high
tensile modulus fibers suitable for the manufacture of ballistic
resistant fabrics. Particularly suitable high-strength, high
tensile modulus fiber materials that are particularly suitable for
the formation of ballistic resistant materials and articles include
polyolefin fibers including high density and low density
polyethylene. Particularly preferred are extended chain polyolefin
fibers, such as highly oriented, high molecular weight polyethylene
fibers, particularly ultra-high molecular weight polyethylene
fibers, and polypropylene fibers, particularly ultra-high molecular
weight polypropylene fibers. Also suitable are aramid fibers,
particularly para-aramid fibers, polyamide fibers, polyethylene
terephthalate fibers, polyethylene naphthalate fibers, extended
chain polyvinyl alcohol fibers, extended chain polyacrylonitrile
fibers, polybenzazole fibers, such as polybenzoxazole (PBO) and
polybenzothiazole (PBT) fibers, liquid crystal copolyester fibers
and rigid rod fibers such as M5.RTM. fibers. Each of these fiber
types is conventionally known in the art. Also suitable for
producing polymeric fibers are copolymers, block polymers and
blends of the above materials.
The most preferred fiber types for ballistic resistant fabrics
include polyethylene, particularly extended chain polyethylene
fibers, aramid fibers, polybenzazole fibers, liquid crystal
copolyester fibers, polypropylene fibers, particularly highly
oriented extended chain polypropylene fibers, polyvinyl alcohol
fibers, polyacrylonitrile fibers and rigid rod fibers, particularly
M5.RTM. fibers.
In the case of polyethylene, preferred fibers are extended chain
polyethylenes having molecular weights of at least 500,000,
preferably at least one million and more preferably between two
million and five million. Such extended chain polyethylene (ECPE)
fibers may be grown in solution spinning processes such as
described in U.S. Pat. Nos. 4,137,394 or 4,356,138, which are
incorporated herein by reference, or may be spun from a solution to
form a gel structure, such as described in U.S. Pat. Nos. 4,551,296
and 5,006,390, which are also incorporated herein by reference. A
particularly preferred fiber type for use in the invention are
polyethylene fibers sold under the trademark SPECTRA.RTM. from
Honeywell International Inc. SPECTRA.RTM. fibers are well known in
the art and are described, for example, in U.S. Pat. Nos. 4,623,547
and 4,748,064.
Also particularly preferred are aramid (aromatic polyamide) or
para-aramid fibers. Such are commercially available and are
described, for example, in U.S. Pat. No. 3,671,542. For example,
useful poly(p-phenylene terephthalamide) filaments are produced
commercially by Dupont corporation under the trademark of
KEVLAR.RTM.. Also useful in the practice of this invention are
poly(m-phenylene isophthalamide) fibers produced commercially by
Dupont under the trademark NOMEX.RTM. and fibers produced
commercially by Teijin under the trademark TWARON.RTM.; aramid
fibers produced commercially by Kolon Industries, Inc. of Korea
under the trademark HERACRON.RTM.; p-aramid fibers SVM.TM. and
RUSAR.TM. which are produced commercially by Kamensk Volokno JSC of
Russia and ARMOS.TM. p-aramid fibers produced commercially by JSC
Chim Volokno of Russia.
Suitable polybenzazole fibers for the practice of this invention
are commercially available and are disclosed for example in U.S.
Pat. Nos. 5,286,833, 5,296,185, 5,356,584, 5,534,205 and 6,040,050,
each of which are incorporated herein by reference. Preferred
polybenzazole fibers are ZYLON.RTM. brand fibers from Toyobo Co.
Suitable liquid crystal copolyester fibers for the practice of this
invention are commercially available and are disclosed, for
example, in U.S. Pat. Nos. 3,975,487; 4,118,372 and 4,161,470, each
of which is incorporated herein by reference.
Suitable polypropylene fibers include highly oriented extended
chain polypropylene (ECPP) fibers as described in U.S. Pat. No.
4,413,110, which is incorporated herein by reference. Suitable
polyvinyl alcohol (PV-OH) fibers are described, for example, in
U.S. Pat. Nos. 4,440,711 and 4,599,267 which are incorporated
herein by reference. Suitable polyacrylonitrile (PAN) fibers are
disclosed, for example, in U.S. Pat. No. 4,535,027, which is
incorporated herein by reference. Each of these fiber types is
conventionally known and is widely commercially available.
The other suitable fiber types for use in the present invention
include rigid rod fibers such as M5.RTM. fibers, and combinations
of all the above materials, all of which are commercially
available. For example, the fibrous layers may be formed from a
combination of SPECTRA.RTM. fibers and Kevlar.RTM. fibers. M5.RTM.
fibers are formed from pyridobisimidazole-2,6-diyl
(2,5-dihydroxy-p-phenylene) and are manufactured by Magellan
Systems International of Richmond, Va. and are described, for
example, in U.S. Pat. Nos. 5,674,969, 5,939,553, 5,945,537, and
6,040,478, each of which is incorporated herein by reference.
Specifically preferred fibers include M5.RTM. fibers, polyethylene
SPECTRA.RTM. fibers, aramid Kevlar.RTM. fibers and aramid
TWARON.RTM. fibers. The fibers may be of any suitable denier, such
as, for example, 50 to about 3000 denier, more preferably from
about 200 to 3000 denier, still more preferably from about 650 to
about 2000 denier, and most preferably from about 800 to about 1500
denier. The selection is governed by considerations of ballistic
effectiveness and cost. Finer fibers are more costly to manufacture
and to weave, but can produce greater ballistic effectiveness per
unit weight.
The most preferred fibers for the purposes of the invention are
either high-strength, high tensile modulus extended chain
polyethylene fibers or high-strength, high tensile modulus
para-aramid fibers. As stated above, a high-strength, high tensile
modulus fiber is one which has a preferred tenacity of about 7
g/denier or more, a preferred tensile modulus of about 150 g/denier
or more and a preferred energy-to-break of about 8 J/g or more,
each as measured by ASTM D2256. In the preferred embodiment of the
invention, the tenacity of the fibers should be about 15 g/denier
or more, preferably about 20 g/denier or more, more preferably
about 25 g/denier or more and most preferably about 30 g/denier or
more. The fibers of the invention also have a preferred tensile
modulus of about 300 g/denier or more, more preferably about 400
g/denier or more, more preferably about 500 g/denier or more, more
preferably about 1,000 g/denier or more and most preferably about
1,500 g/denier or more. The fibers of the invention also have a
preferred energy-to-break of about 15 J/g or more, more preferably
about 25 J/g or more, more preferably about 30 J/g or more and most
preferably have an energy-to-break of about 40 J/g or more.
These combined high strength properties are obtainable by employing
well known processes. U.S. Pat. Nos. 4,413,110, 4,440,711,
4,535,027, 4,457,985, 4,623,547 4,650,710 and 4,748,064 generally
discuss the formation of preferred high strength, extended chain
polyethylene fibers employed in the present invention. Such
methods, including solution grown or gel fiber processes, are well
known in the art. Methods of forming each of the other preferred
fiber types, including para-aramid fibers, are also conventionally
known in the art, and the fibers are commercially available.
In accordance with the invention, a multilayer coating is applied
onto at least part of a surface of the fiber or fabric substrates
described herein. The multilayer coating comprises a first polymer
layer directly on a surface of said fibers, and a second polymer
layer on said first polymer layer, wherein the first polymer layer
and the second polymer layer are different. One or both of the
first polymer and/or second polymer may function as a binder
material that binds a plurality of fibers together by way of their
adhesive characteristics or after being subjected to well known
heat and/or pressure conditions. In accordance with the invention,
at least one of the first polymer layer and the second polymer
layer comprises a fluorine-containing polymer. While both the first
polymer layer and the second polymer layer may comprise different
fluorine-containing polymers, it is most preferred that only one of
said layers comprises a fluorine-containing polymer, while the
other is substantially absent of fluorine. In the most preferred
embodiment of the invention, the first polymer layer comprises a
fluorine-containing polymer and the second polymer layer is
substantially absent of fluorine. Additional polymer layers may
also be coated onto the fibers, where each additional polymer layer
is preferably coated onto the last applied polymer layer. The
optional additional polymer layers may be the same as or different
than the first polymer layer and/or the second polymer layer.
It has been found that polymers containing fluorine atoms,
particularly fluoropolymers and/or a fluorocarbon resins, are
desirable because of their resistance to dissolution, permeation
and/or transpiration by water and resistance to dissolution,
permeation and/or transpiration by one or more organic solvents.
Importantly, when fluorine-containing polymers are applied onto
ballistic resistant fibers together with another polymeric material
that is conventionally used in the art of ballistic resistant
fabrics as a polymeric matrix material, the ballistic performance
of a ballistic resistant composite formed therefrom is
substantially retained after the composite is immersed in either
water, e.g. salt water, or gasoline.
More specifically, it has been found that fabrics including fibers
coated with a layer of a fluorine-containing polymer and a
separately applied layer of a conventional matrix polymer have a
significantly improved V.sub.50 retention % after immersion in
either salt water or gasoline, i.e. greater than 90% retention as
illustrated in the inventive examples, compared to fabrics formed
with only non-fluorine-containing polymeric materials. Such
materials also have a significantly reduced tendency to absorb
either salt water or gasoline compared to fabrics formed without a
fluorine-containing polymer layer, as the fluorine-containing
polymer serves as a barrier between individual filaments, fibers
and/or fabrics and salt water or gasoline.
Fluorine-containing materials, particularly fluoropolymers and
fluorocarbon resin materials, are commonly known for their
excellent chemical resistance and moisture barrier properties.
Useful fluoropolymer and fluorocarbon resin materials herein
include fluoropolymer homopolymers, fluoropolymer copolymers or
blends thereof as are well known in the art and are described in,
for example, U.S. Pat. Nos. 4,510,301, 4,544,721 and 5,139,878.
Examples of useful fluoropolymers include, but are not limited to,
homopolymers and copolymers of chlorotrifluoroethylene,
ethylene-chlorotrifluoroethylene copolymers,
ethylene-tetrafluoroethylene copolymers, fluorinated
ethylene-propylene copolymers, perfluoroalkoxyethylene,
polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinyl
fluoride, polyvinylidene fluoride, and copolymers and blends
thereof.
As used herein, copolymers include polymers having two or more
monomer components. Preferred fluoropolymers include homopolymers
and copolymers of polychlorotrifluoroethylene. Particularly
preferred are polychlorotrifluoroethylene (PCTFE) homopolymer
materials sold under the ACLON.TM. trademark and which are
commercially available from Honeywell International Inc. of
Morristown, New Jersey. The most preferred fluoropolymers or
fluorocarbon resins include fluorocarbon-modified polymers,
particularly fluoro-oligomers and fluoropolymers formed by grafting
fluorocarbon side-chains onto conventional polyethers (i.e.
fluorocarbon-modified polyethers), polyesters (i.e.
fluorocarbon-modified polyesters), polyanions (i.e.
fluorocarbon-modified polyanions) such as polyacrylic acid (i.e.
fluorocarbon-modified polyacrylic acid) or polyacrylates (i.e.
fluorocarbon-modified polyacrylates), and polyurethanes (i.e.
fluorocarbon-modified polyurethanes). These fluorocarbon side
chains or perfluoro compounds are generally produced by a
telomerization process and are referred to as C.sub.8
fluorocarbons. For example, a fluoropolymer or fluorocarbon resin
may be derived from the telomerization of an unsaturated
fluoro-compound, forming a fluorotelomer, where said fluorotelomer
is further modified to allow reaction with a polyether, polyester,
polyanion, polyacrylic acid, polyacrylate or polyurethane, and
where the fluorotelomer is then grafted onto a polyether,
polyester, polyanion, polyacrylic acid, polyacrylate or
polyurethane. Good representative examples of these
fluorocarbon-containing polymers are NUVA.RTM. fluoropolymer
products, commercially available from Clariant International, Ltd.
of Switzerland. Other fluorocarbon resins, fluoro-oligomers and
fluoropolymers having perfluoro acid-based and perfluoro
alcohol-based side chains are also most preferred. Fluoropolymers
and fluorocarbon resins having fluorocarbon side chains of shorter
lengths, such as C.sub.6, C.sub.4 or C.sub.2, are also suitable,
such as POLYFOX.TM. fluorochemicals, commercially available from
Omnova Solutions, Inc. of Fairlawn, Ohio.
The fluorine-containing polymeric material may also comprise a
combination of a fluoropolymer or a fluorocarbon-containing
material with another polymer, including blends of
fluorine-containing polymeric materials with conventional polymeric
binder (matrix) materials such as those described herein. In one
preferred embodiment, the polymer layer comprising a
fluorine-containing polymer is a blend of a fluorine-containing
polymer and an acrylic polymer. Preferred acrylic polymers
non-exclusively include acrylic acid esters, particularly acrylic
acid esters derived from monomers such as methyl acrylate, ethyl
acrylate, n-propyl acrylate, 2-propyl acrylate, n-butyl acrylate,
2-butyl acrylate and tert-butyl acrylate, hexyl acrylate, octyl
acrylate and 2-ethylhexyl acrylate. Preferred acrylic polymers also
particularly include methacrylic acid esters derived from monomers
such as methyl methacrylate, ethyl methacrylate, n-propyl
methacrylate, 2-propyl methacrylate, n-butyl methacrylate, 2-butyl
methacrylate, tert-butyl methacrylate, hexyl methacrylate, octyl
methacrylate and 2-ethylhexyl methacrylate. Copolymers and
terpolymers made from any of these constituent monomers are also
preferred, along with those also incorporating acrylamide,
n-methylol acrylamide, acrylonitrile, methacrylonitrile, acrylic
acid and maleic anhydride. Also suitable are modified acrylic
polymers modified with non-acrylic monomers. For example, acrylic
copolymers and acrylic terpolymers incorporating suitable vinyl
monomers such as: (a) olefins, including ethylene, propylene and
isobutylene; (b) styrene, N-vinylpyrrolidone and vinylpyridine; (c)
vinyl ethers, including vinyl methyl ether, vinyl ethyl ether and
vinyl n-butyl ether; (d) vinyl esters of aliphatic carboxylic
acids, including vinyl acetate, vinyl propionate, vinyl butyrate,
vinyl laurate and vinyl decanoates; and (f) vinyl halides,
including vinyl chloride, vinylidene chloride, ethylene dichloride
and propenyl chloride. Vinyl monomers which are likewise suitable
are maleic acid diesters and fumaric acid diesters, in particular
of monohydric alkanols having 2 to 10 carbon atoms, preferably 3 to
8 carbon atoms, including dibutyl maleate, dihexyl maleate, dioctyl
maleate, dibutyl fumarate, dihexyl fumarate and dioctyl
fumarate.
Acrylic polymers and copolymers are preferred because of their
inherent hydrolytic stability, which is due to the straight carbon
backbone of these polymers. Acrylic polymers are also preferred
because of the wide range of physical properties available in
commercially produced materials. The range of physical properties
available in acrylic resins matches, and perhaps exceeds, the range
of physical properties thought to be desirable in polymeric binder
materials of ballistic resistant composite matrix resins.
One of the first polymer layer or the second polymer layer
preferably comprises a non-fluorine containing, i.e. substantially
absent of fluorine, polymeric material that is conventionally
employed in the art of ballistic resistant fabrics as a polymeric
binder (matrix) material. Most preferably, the second polymer layer
is formed from a non-fluorine-containing polymeric material. A wide
variety of conventional, non-fluorine-containing polymeric binder
materials are known in the art. Such include both low modulus,
elastomeric materials and high modulus, rigid materials. Preferred
low modulus, elastomeric materials are those having an initial
tensile modulus less than about 6,000 psi (41.3 MPa), and preferred
high modulus, rigid materials are those having an initial tensile
modulus at least about 100,000 psi (689.5 MPa), each as measured at
37.degree. C. by ASTM D638. As used herein throughout, the term
tensile modulus means the modulus of elasticity as measured by ASTM
2256 for a fiber and by ASTM D638 for a polymeric binder
material.
An elastomeric polymeric binder material may comprise a variety of
materials. A preferred elastomeric binder material comprises a low
modulus elastomeric material. For the purposes of this invention, a
low modulus elastomeric material has a tensile modulus, measured at
about 6,000 psi (41.4 MPa) or less according to ASTM D638 testing
procedures. Preferably, the tensile modulus of the elastomer is
about 4,000 psi (27.6 MPa) or less, more preferably about 2400 psi
(16.5 MPa) or less, more preferably 1200 psi (8.23 MPa) or less,
and most preferably is about 500 psi (3.45 MPa) or less. The glass
transition temperature (Tg) of the elastomer is preferably about
0.degree. C. or less, more preferably about -40.degree. C. or less,
and most preferably about -50.degree. C. or less. The elastomer
also has a preferred elongation to break of at least about 50%,
more preferably at least about 100% and most preferably has an
elongation to break of at least about 300%.
A wide variety of materials and formulations having a low modulus
may be utilized as a non-fluorine-containing polymeric binder
material. Representative examples include polybutadiene,
polyisoprene, natural rubber, ethylene-propylene copolymers,
ethylene-propylene-diene terpolymers, polysulfide polymers,
polyurethane elastomers, chlorosulfonated polyethylene,
polychloroprene, plasticized polyvinylchloride, butadiene
acrylonitrile elastomers, poly(isobutylene-co-isoprene),
polyacrylates, polyesters, polyethers, silicone elastomers,
copolymers of ethylene, and combinations thereof, and other low
modulus polymers and copolymers. Also preferred are blends of
different elastomeric materials, or blends of elastomeric materials
with one or more thermoplastics.
Particularly useful are block copolymers of conjugated dienes and
vinyl aromatic monomers. Butadiene and isoprene are preferred
conjugated diene elastomers. Styrene, vinyl toluene and t-butyl
styrene are preferred conjugated aromatic monomers. Block
copolymers incorporating polyisoprene may be hydrogenated to
produce thermoplastic elastomers having saturated hydrocarbon
elastomer segments. The polymers may be simple tri-block copolymers
of the type A-B-A, multi-block copolymers of the type (AB).sub.n
(n=2-10) or radial configuration copolymers of the type
R-(BA).sub.x (x=3-150); wherein A is a block from a polyvinyl
aromatic monomer and B is a block from a conjugated diene
elastomer. Many of these polymers are produced commercially by
Kraton Polymers of Houston, Tex. and described in the bulletin
"Kraton Thermoplastic Rubber", SC-68-81. The most preferred low
modulus polymeric binder materials comprise styrenic block
copolymers, particularly polystyrene-polyisoprene-polystyrene-block
copolymers, sold under the trademark KRATON.RTM. commercially
produced by Kraton Polymers and HYCAR.RTM. T122 acrylic resins
commercially available from Noveon, Inc. of Cleveland, Ohio.
Preferred high modulus, rigid polymers useful as the other,
preferably non-fluorine-containing polymeric binder material
include materials such as a vinyl ester polymer or a
styrene-butadiene block copolymer, and also mixtures of polymers
such as vinyl ester and diallyl phthalate or phenol formaldehyde
and polyvinyl butyral. A particularly preferred high modulus
material is a thermosetting polymer, preferably soluble in
carbon-carbon saturated solvents such as methyl ethyl ketone, and
possessing a high tensile modulus when cured of at least about
1.times.10.sup.5 psi (689.5 MPa) as measured by ASTM D638.
Particularly preferred rigid materials are those described in U.S.
Pat. No. 6,642,159, which is incorporated herein by reference.
In the preferred embodiments of the invention, either the first
polymer layer or the second polymer layer, most preferably the
second polymer layer, comprises a polyurethane polymer, a polyether
polymer, a polyester polymer, a polycarbonate resin, a polyacetal
polymer, a polyamide polymer, a polybutylene polymer, an
ethylene-vinyl acetate copolymer, an ethylene-vinyl alcohol
copolymer, an ionomer, a styrene-isoprene copolymer, a
styrene-butadiene copolymer, a styrene-ethylene/butylene copolymer,
a styrene-ethylene/propylene copolymer, a polymethyl pentene
polymer, a hydrogenated styrene-ethylene/butylene copolymer, a
maleic anhydride functionalized styrene-ethylene/butylene
copolymer, a carboxylic acid functionalized
styrene-ethylene/butylene copolymer, an acrylonitrile polymer, an
acrylonitrile butadiene styrene copolymer, a polypropylene polymer,
a polypropylene copolymer, an epoxy resin, a novolac resin, a
phenolic resin, a vinyl ester resin, a silicone resin, a nitrile
rubber polymer, a natural rubber polymer, a cellulose acetate
butyrate polymer, a polyvinyl butyral polymer, an acrylic polymer,
an acrylic copolymer or an acrylic copolymer incorporating
non-acrylic monomers.
The rigidity, impact and ballistic properties of the articles
formed from the fibrous composites of the invention are affected by
the tensile modulus of the binder polymers coating the fibers. For
example, U.S. Pat. No. 4,623,574 discloses that fiber reinforced
composites constructed with elastomeric matrices having tensile
moduli less than about 6000 psi (41,300 kPa) have superior
ballistic properties compared both to composites constructed with
higher modulus polymers, and also compared to the same fiber
structure without one or more coatings of a polymeric binder
material. However, low tensile modulus polymeric binder polymers
also yield lower rigidity composites. Further, in certain
applications, particularly those where a composite must function in
both anti-ballistic and structural modes, there is needed a
superior combination of ballistic resistance and rigidity.
Accordingly, the most appropriate type of non-fluorine-containing
polymeric binder material to be used will vary depending on the
type of article to be formed from the fabrics of the invention. In
order to achieve a compromise in both properties, a suitable
non-fluorine containing material may combine both low modulus and
high modulus materials to form a single polymeric binder material
for use as the first polymer layer, as the second polymer layer or
as any additional polymer layer. Each polymer layer may also
include fillers such as carbon black or silica, may be extended
with oils, or may be vulcanized by sulfur, peroxide, metal oxide or
radiation cure systems if appropriate, as is well known in the
art.
The application of the multilayer coating is conducted prior to
consolidating multiple fiber plies, and the multilayer coating is
to be applied on top of any pre-existing fiber finish, such as a
spin finish. The fibers of the invention may be coated on,
impregnated with, embedded in, or otherwise applied with each
polymer layer by applying each layer to the fibers, followed by
consolidating the coated fiber layers to form a composite. The
individual fibers are coated either sequentially or consecutively.
Each polymer layer is preferably first applied onto a plurality of
fibers followed by forming either a woven fabric or at least one
non-woven fiber ply from said fibers. In a preferred embodiment, a
plurality of individual fibers are provided as a fiber web, wherein
a first polymer layer is applied onto the fiber web, and thereafter
a second polymer layer is applied onto the first polymer layer on
the fiber web. Thereafter, the coated fiber web is preferably
formed into a fabric.
Alternately, a plurality of fibers may first be arranged into a
fabric and subsequently coated, or at least one non-woven fiber ply
may be formed first followed by applying each polymer layer onto
each fiber ply. In another embodiment, the fibrous substrate is a
woven fabric wherein uncoated fibers are first woven into a woven
fabric, which fabric is subsequently coated with each polymer
layer. It should be understood that the invention also encompasses
other methods of producing fibrous substrates having the multilayer
coatings described herein. For example, a plurality of fibers may
first be coated with a first polymer layer, followed by forming a
woven or non-woven fabric from said fibers, and subsequently
applying a second polymer layer onto the first polymer layer on the
woven or non-woven fabric. In the most preferred embodiment of the
invention, the fibers of the invention are first coated with each
polymeric binder material, followed by arranging a plurality of
fibers into either a woven or non-woven fabric. Such techniques are
well known in the art.
For the purposes of the present invention, the term "coated" is not
intended to limit the method by which the polymer layers are
applied onto the fibrous substrate surface. Any appropriate method
of applying the polymer layers onto substrates may be utilized
where the first polymer layer is applied first, followed by
subsequently applying the second polymer layer onto the first
polymer layer. For example, the polymer layers may be applied in
solution form by spraying or roll coating a solution of the
polymeric material onto fiber surfaces, wherein a portion of the
solution comprises the desired polymer or polymers and a portion of
the solution comprises a solvent capable of dissolving the polymer
or polymers, followed by drying. Another method is to apply a neat
polymer of each coating material to fibers either as a liquid, a
sticky solid or particles in suspension or as a fluidized bed.
Alternatively, each coating may be applied as a solution, emulsion
or dispersion in a suitable solvent which does not adversely affect
the properties of fibers at the temperature of application. For
example, the fibrous substrate can be transported through a
solution of the polymeric binder material to substantially coat the
substrate with a first polymeric material and then dried to form a
coated fibrous substrate, followed by similarly coating with a
second different polymeric material. The resulting multilayer
coated fiber is then arranged into the desired configuration. In
another coating technique, fiber plies or woven fabrics may first
be arranged, followed by dipping the plies or fabrics into a bath
of a solution containing the first polymeric binder material
dissolved in a suitable solvent, such that each individual fiber is
at least partially coated with the polymeric binder material, and
then dried through evaporation or volatilization of the solvent,
and subsequently the second polymer layer may be applied via the
same method. The dipping procedure may be repeated several times as
required to place a desired amount of polymeric material onto the
fibers, preferably encapsulating each of the individual fibers or
covering all or substantially all of the fiber surface area with
the polymeric material.
Other techniques for applying the coating to the fibers may be
used, including coating of the high modulus precursor (gel fiber)
before the fibers are subjected to a high temperature stretching
operation, either before or after removal of the solvent from the
fiber (if using a gel-spinning fiber forming technique). The fiber
may then be stretched at elevated temperatures to produce the
coated fibers. The gel fiber may be passed through a solution of
the appropriate coating polymer under conditions to attain the
desired coating. Crystallization of the high molecular weight
polymer in the gel fiber may or may not have taken place before the
fiber passes into the solution. Alternatively, the fibers may be
extruded into a fluidized bed of an appropriate polymeric powder.
Furthermore, if a stretching operation or other manipulative
process, e.g. solvent exchanging, drying or the like is conducted,
the coating may be applied to a precursor material of the final
fibers. Additionally, the first polymer layer and the second
polymer layer may be applied using two different methods.
Preferably, the first and second polymer layers are each applied to
the fibrous substrate surfaces when the polymers forming said
layers are wet, i.e. in the liquid state. Most preferably, the
first polymer and the second polymer are contacted with each other
as liquids. In other words, the second polymer is preferably
applied onto the fibrous substrate as a liquid while the first
polymer is wet. Wet application is preferred because at least one
of the first polymer layer or the second polymer layer is formed
from a fluorine-containing polymer, which are commonly difficult to
attach to layers formed from non-fluorine-containing polymers. The
wet application of each polymer facilitates interlayer adhesion of
the different polymer layers, wherein the individual layers are
unified at the surfaces where they contact each other as polymer
molecules from the polymer layers commingle with each other at
their contact surfaces and at least partially fuse together. For
the purposes of the invention, a liquid polymer includes polymers
that are combined with a solvent or other liquid capable of
dissolving or dispersing a polymer, as well as molten polymers that
are not combined with a solvent or other liquid.
While any liquid capable of dissolving or dispersing a polymer may
be used, preferred groups of solvents include water, paraffin oils
and aromatic solvents or hydrocarbon solvents, with illustrative
specific solvents including paraffin oil, xylene, toluene, octane,
cyclohexane, methyl ethyl ketone (MEK) and acetone. The techniques
used to dissolve or disperse the coating polymers in the solvents
will be those conventionally used for the coating of similar
materials on a variety of substrates.
It is known that fluorine-containing polymer layers can be
difficult to adhere to non-fluorine-containing polymer layers. In
general, fluorine-containing solid surfaces are difficult to wet or
adhere with a non-fluorine containing liquid. This can be an issue
when attempting to coat fibers that are already coated with a
fluorine-containing finish with a conventional liquid matrix resin.
In other arts, it is known to use special intermediate adhesive tie
layers to attach the dissimilar layers, but such adhesive tie
layers are undesirable for use in ballistic resistant composites as
they may detrimentally affect the properties of the composites.
However, it has been found that multiple layers of dissimilar
polymeric matrix materials may be applied onto fibers without using
an adhesive tie layer. Particularly, it has been found that wet
fluorine-containing liquids and wet non-fluorine-containing liquids
are miscible and will wet each other when they are brought
together. Accordingly, such wet dissimilar materials may be applied
onto a fiber surface and be effectively adhered to each other and
to the surface of a fibrous substrate.
In a most preferred method that has been found to be effective, the
first polymer layer and the second polymer layer are first applied
onto separate substrates, followed by bringing the substrates
together to contact the polymer layers with each other. Most
preferably, this method comprises: applying the first polymer onto
a surface of a fibrous substrate; applying the second polymer onto
a surface of a support; thereafter, joining the fibrous substrate
and the support to contact the first polymer with the second
polymer; and then separating the support from the fibrous
substrate, such that at least a portion of the second polymer is
transferred from the support onto the first polymer. The support
may be any solid substrate that is capable of supporting a polymer
layer, such as a silicone-coated release liner, a solid film or
another fabric. The support may also comprise a conveyor belt that
is an integral part of utilized fabric processing equipment. The
support must be capable of transferring at least a portion of the
second polymer onto the first polymer. This method is especially
attractive for the application of layers of dissimilar polymeric
materials onto fibrous substrates without regard to chemical or
physical incompatibilities of the dissimilar polymeric materials. A
preferred method for conducting this technique is described in the
examples below and illustrated in FIG. 1.
Generally, a polymeric binder coating is necessary to efficiently
merge, i.e. consolidate, a plurality of fiber plies. The multilayer
matrix coating may be applied onto the entire surface area of the
fibers, or only onto a partial surface area of the fibers. Most
preferably, the multilayer matrix coating is applied onto
substantially all the surface area of each component fiber of a
woven or non-woven fabric of the invention. Where the fabrics
comprise a plurality of yarns, each fiber forming a single strand
of yarn is preferably coated with the multilayer polymeric binder
coating.
When the fibrous substrate is an individual fiber, a plurality of
individual fibers may be coated with the multilayer coating either
sequentially or consecutively, and thereafter may be organized into
one or more non-woven fiber plies, a non-woven fabric, or woven
into a fabric. With regard to woven fabrics, while the matrix
coatings may be applied either before or after the fibers are
woven, it is most preferred that the matrix coatings be applied
after fibers are woven into a fabric due to potential processing
limitations. With regard to non-woven fabrics, it is preferred that
the polymer coatings be applied before the fibers are formed into a
non-woven fabric.
The fibers may be formed into non-woven fabrics which comprise a
plurality of overlapping, non-woven fibrous plies that are
consolidated into a single-layer, monolithic element. In this
embodiment, each ply comprises an arrangement of non-overlapping
fibers that are aligned in a unidirectional, substantially parallel
array. This type of fiber arrangement is known in the art as a
"unitape" (unidirectional tape) and is referred to herein as a
"single ply". As used herein, an "array" describes an orderly
arrangement of fibers or yarns, and a "parallel array" describes an
orderly parallel arrangement of fibers or yarns. A fiber "layer"
describes a planar arrangement of woven or non-woven fibers or
yarns including one or more plies. As used herein, a "single-layer"
structure refers to monolithic structure composed of one or more
individual fiber plies that have been consolidated into a single
unitary structure. By "consolidating" it is meant that the
multilayer polymeric binder coating together with each fiber ply
are combined into a single unitary layer. Consolidation can occur
via drying, cooling, heating, pressure or a combination thereof.
Heat and/or pressure may not be necessary, as the fibers or fabric
layers may just be glued together, as is the case in a wet
lamination process. The term "composite" refers to combinations of
fibers with the multilayer polymeric binder material. Such is
conventionally known in the art.
A preferred non-woven fabric of the invention includes a plurality
of stacked, overlapping fiber plies (plurality of unitapes) wherein
the parallel fibers of each single ply (unitape) are positioned
orthogonally (0.degree./90.degree.) to the parallel fibers of each
adjacent single ply relative to the longitudinal fiber direction of
each single ply. The stack of overlapping non-woven fiber plies is
consolidated under heat and pressure, or by adhering the polymeric
resin coatings of individual fiber plies, to form a single-layer,
monolithic element which has also been referred to in the art as a
single-layer, consolidated network where a "consolidated network"
describes a consolidated (merged) combination of fiber plies with a
polymeric binder material. The terms "polymeric binder" and
"polymeric matrix" are used interchangeably herein, and describe a
material that binds fibers together. These terms are conventionally
known in the art, and refer to a multilayer material herein.
As is conventionally known in the art, excellent ballistic
resistance is achieved when individual fiber plies are cross-plied
such that the fiber alignment direction of one ply is rotated at an
angle with respect to the fiber alignment direction of another ply.
Most preferably, the fiber plies are cross-plied orthogonally at
0.degree. and 90.degree. angles, but adjacent plies can be aligned
at virtually any angle between about 0.degree. and about 90.degree.
with respect to the longitudinal fiber direction of another ply.
For example, a five ply non-woven structure may have plies oriented
at a 0.degree./45.degree./90.degree./45.degree./0.degree. or at
other angles. Such rotated unidirectional alignments are described,
for example, in U.S. Pat. Nos. 4,457,985; 4,748,064; 4,916,000;
4,403,012; 4,623,573; and 4,737,402.
Most typically, non-woven fabrics include from 1 to about 6 plies,
but may include as many as about 10 to about 20 plies as may be
desired for various applications. The greater the number of plies
translates into greater ballistic resistance, but also greater
weight. Accordingly, the number of fiber plies forming a fabric or
an article of the invention varies depending upon the ultimate use
of the fabric or article. For example, in body armor vests for
military applications, in order to form an article composite that
achieves a desired 1.0 pound per square foot areal density (4.9
kg/m.sup.2), a total of at 22 individual plies may be required,
wherein the plies may be woven, knitted, felted or non-woven
fabrics (with parallel oriented fibers or other arrangements)
formed from the high-strength fibers described herein. In another
embodiment, body armor vests for law enforcement use may have a
number of plies based on the National Institute of Justice (NIJ)
Threat Level. For example, for an NIJ Threat Level IIIA vest, there
may also be a total of 22 plies. For a lower NIJ Threat Level,
fewer plies may be employed.
Further, the fiber plies of the invention may alternately comprise
yarns rather than fibers, where a "yarn" is a strand consisting of
multiple fibers or filaments. Non-woven fiber plies may alternately
comprise other fiber arrangements, such as felted structures which
are formed using conventionally known techniques, comprising fibers
in random orientation instead of parallel arrays. Articles of the
invention may also comprise combinations of woven fabrics,
non-woven fabrics formed from unidirectional fiber plies and
non-woven felt fabrics.
Consolidated non-woven fabrics may be constructed using well known
methods, such as by the methods described in U.S. Pat. No.
6,642,159, the disclosure of which is incorporated herein by
reference. As is well known in the art, consolidation is done by
positioning the individual fiber plies on one another under
conditions of sufficient heat and pressure to cause the plies to
combine into a unitary fabric. Consolidation may be done at
temperatures ranging from about 50.degree. C. to about 175.degree.
C., preferably from about 105.degree. C. to about 175.degree. C.,
and at pressures ranging from about 5 psig (0.034 MPa) to about
2500 psig (17 MPa), for from about 0.01 seconds to about 24 hours,
preferably from about 0.02 seconds to about 2 hours. When heating,
it is possible that the polymeric binder coatings can be caused to
stick or flow without completely melting. However, generally, if
the polymeric binder materials are caused to melt, relatively
little pressure is required to form the composite, while if the
binder materials are only heated to a sticking point, more pressure
is typically required. As is conventionally known in the art,
consolidation may be conducted in a calender set, a flat-bed
laminator, a press or in an autoclave.
Alternately, consolidation may be achieved by molding under heat
and pressure in a suitable molding apparatus. Generally, molding is
conducted at a pressure of from about 50 psi (344.7 kPa) to about
5000 psi (34470 kPa), more preferably about 100 psi (689.5 kPa) to
about 1500 psi (10340 kPa), most preferably from about 150 psi
(1034 kPa) to about 1000 psi (6895 kPa). Molding may alternately be
conducted at higher pressures of from about 500 psi (3447 kPa) to
about 5000 psi, more preferably from about 750 psi (5171 kPa) to
about 5000 psi and more preferably from about 1000 psi to about
5000 psi. The molding step may take from about 4 seconds to about
45 minutes. Preferred molding temperatures range from about
200.degree. F. (.about.93.degree. C.) to about 350.degree. F.
(.about.177.degree. C.), more preferably at a temperature from
about 200.degree. F. to about 300.degree. F. (.about.149.degree.
C.) and most preferably at a temperature from about 200.degree. F.
to about 280.degree. F. (.about.121.degree. C.). The pressure under
which the fabrics of the invention are molded has a direct effect
on the stiffness or flexibility of the resulting molded product.
Particularly, the higher the pressure at which the fabrics are
molded, the higher the stiffness, and vice-versa. In addition to
the molding pressure, the quantity, thickness and composition of
the fabric plies and polymeric binder coating types also directly
affects the stiffness of the articles formed from the inventive
fabrics.
While each of the molding and consolidation techniques described
herein are similar, each process is different. Particularly,
molding is a batch process and consolidation is a continuous
process. Further, molding typically involves the use of a mold,
such as a shaped mold or a match-die mold when forming a flat
panel, and does not necessarily result in a planar product.
Normally consolidation is done in a flat-bed laminator, a calendar
nip set or as a wet lamination to produce soft body armor fabrics.
Molding is typically reserved for the manufacture of hard armor,
e.g. rigid plates. In the context of the present invention,
consolidation techniques and the formation of soft body armor are
preferred.
In either process, suitable temperatures, pressures and times are
generally dependent on the type of polymeric binder coating
materials, polymeric binder content (of the combined coatings),
process used and fiber type. The fabrics of the invention may
optionally be calendered under heat and pressure to smooth or
polish their surfaces. Calendering methods are well known in the
art.
Woven fabrics may be formed using techniques that are well known in
the art using any fabric weave, such as plain weave, crowfoot
weave, basket weave, satin weave, twill weave and the like. Plain
weave is most common, where fibers are woven together in an
orthogonal 0.degree./90.degree. orientation. In another embodiment,
a hybrid structure may be assembled where one both woven and
non-woven fabrics are combined and interconnected, such as by
consolidation. Prior to weaving, the individual fibers of each
woven fabric material may or may not be coated with the first
polymer layer and second polymer layer, or other additional polymer
layers.
To produce a fabric article having sufficient ballistic resistance
properties, the proportion of fibers forming the fabric preferably
comprises from about 50% to about 98% by weight of the fibers plus
the weight of the combined polymeric coatings, more preferably from
about 70% to about 95%, and most preferably from about 78% to about
90% by weight of the fibers plus the polymeric coatings. Thus, the
total weight of the combined polymeric coatings preferably
comprises from about 2% to about 50% by weight of the fabric, more
preferably from about 5% to about 30% and most preferably from
about 10% to about 22% by weight of the fabric, wherein 16% is most
preferred.
The thickness of the individual fabrics will correspond to the
thickness of the individual fibers. A preferred woven fabric will
have a preferred thickness of from about 25 .mu.m to about 500
.mu.m per layer, more preferably from about 50 .mu.m to about 385
.mu.m and most preferably from about 75 .mu.m to about 255 .mu.m
per layer. A preferred non-woven fabric, i.e. a non-woven,
single-layer, consolidated network, will have a preferred thickness
of from about 12 .mu.m to about 500 .mu.m, more preferably from
about 50 .mu.m to about 385 .mu.m and most preferably from about 75
.mu.m to about 255 .mu.m, wherein a single-layer, consolidated
network typically includes two consolidated plies (i.e. two
unitapes). While such thicknesses are preferred, it is to be
understood that other thicknesses may be produced to satisfy a
particular need and yet fall within the scope of the present
invention.
The fabrics of the invention will have a preferred areal density of
from about 50 grams/m.sup.2 (gsm) (0.01 lb/ft.sup.2 (psf)) to about
1000 gsm (0.2 psf). More preferable areal densities for the fabrics
of this invention will range from about 70 gsm (0.014 psf) to about
500 gsm (0.1 psf). The most preferred areal density for fabrics of
this invention will range from about 100 gsm (0.02 psf) to about
250 gsm (0.05 psf). The articles of the invention, which comprise
multiple individual layers of fabric stacked one upon the other,
will further have a preferred areal density of from about 1000 gsm
(0.2 psf) to about 40,000 gsm (8.0 psf), more preferably from about
2000 gsm (0.40 psf) to about 30,000 gsm (6.0 psf), more preferably
from about 3000 gsm (0.60 psf) to about 20,000 gsm (4.0 psf), and
most preferably from about 3750 gsm (0.75 psf) to about 10,000 gsm
(2.0 psf).
The composites of the invention may be used in various applications
to form a variety of different ballistic resistant articles using
well known techniques. For example, suitable techniques for forming
ballistic resistant articles are described in, for example, U.S.
Pat. Nos. 4,623,574, 4,650,710, 4,748,064, 5,552,208, 5,587,230,
6,642,159, 6,841,492 and 6,846,758. The composites are particularly
useful for the formation of flexible, soft armor articles,
including garments such as vests, pants, hats, or other articles of
clothing, and covers or blankets, used by military personnel to
defeat a number of ballistic threats, such as 9 mm full metal
jacket (FMJ) bullets and a variety of fragments generated due to
explosion of hand-grenades, artillery shells, Improvised Explosive
Devices (IED) and other such devises encountered in a military and
peace keeping missions. As used herein, "soft" or "flexible" armor
is armor that does not retain its shape when subjected to a
significant amount of stress and is incapable of being
free-standing without collapsing. The composites are also useful
for the formation of rigid, hard armor articles. By "hard" armor is
meant an article, such as helmets, panels for military vehicles, or
protective shields, which have sufficient mechanical strength so
that it maintains structural rigidity when subjected to a
significant amount of stress and is capable of being freestanding
without collapsing. Fabric composites can be cut into a plurality
of discrete sheets and stacked for formation into an article or
they can be formed into a precursor which is subsequently used to
form an article. Such techniques are well known in the art.
Garments may be formed from the composites of the invention through
methods conventionally known in the art. Preferably, a garment may
be formed by adjoining the ballistic resistant fabric composites of
the invention with an article of clothing. For example, a vest may
comprise a generic fabric vest that is adjoined with the ballistic
resistant composites of the invention, whereby the inventive
composites are inserted into strategically placed pockets. This
allows for the maximization of ballistic protection, while
minimizing the weight of the vest. As used herein, the terms
"adjoining" or "adjoined" are intended to include attaching, such
as by sewing or adhering and the like, as well as un-attached
coupling or juxtaposition with another fabric, such that the
ballistic resistant materials may optionally be easily removable
from the vest or other article of clothing. Articles used in
forming flexible structures like flexible sheets, vests and other
garments are preferably formed from using a low tensile modulus
binder material for the non-fluorine-containing polymer layer. Hard
articles like helmets and armor are preferably formed using a high
tensile modulus binder material for the non-fluorine-containing
polymer layer.
Ballistic resistance properties are determined using standard
testing procedures that are well known in the art. Particularly,
the protective power or penetration resistance of a ballistic
resistant composite is normally expressed by citing the impacting
velocity at which 50% of the projectiles penetrate the composite
while 50% are stopped by the shield, also known as the V.sub.50
value. As used herein, the "penetration resistance" of an article
is the resistance to penetration by a designated threat, such as
physical objects including bullets, fragments, shrapnel and the
like, and non-physical objects, such as a blast from explosion. For
composites of equal areal density, which is the weight of the
composite divided by its area, the higher the V.sub.50, the better
the ballistic resistance of the composite. The ballistic resistant
properties of the articles of the invention will vary depending on
many factors, particularly the type of fibers used to manufacture
the fabrics, the percent by weight of the fibers in the composite,
the suitability of the physical properties of the matrix materials,
the number of layers of fabric making up the composite and the
total areal density of the composite. However, the use of one or
more polymeric coatings that are resistant to dissolution or
penetration by sea water, and resistant to dissolution or
penetration by one or more organic solvents, does not negatively
affect the ballistic properties of the articles of the
invention.
The following examples serve to illustrate the invention:
EXAMPLE 1
A silicone-coated release paper support was coated with a polymeric
binder material that was a water-based acrylic dispersion of
HYCAR.RTM. T122 (commercially available from Noveon, Inc. of
Cleveland, Ohio) using a standard pan-fed reverse roll coating
method. The polymeric binder material was applied at full
strength.
Separately, a fibrous web comprising aramid yarns (TWARON.RTM.
1000-denier, type 2000 aramid yarns, commercially available from
Teijin Twaron BV of The Netherlands) was coated with a dilute
water-based dispersion of a fluorine-containing resin (NUVA.RTM.
LB, commercially available from Clariant International, Ltd. of
Switzerland; dilution: 10% of Nuva LB, 90% de-ionized water) in a
yarn impregnator using a dip and squeeze technique.
A schematic illustration of this hybrid coating technique is
provided in FIG. 1. In the pan-fed reverse roll coating method, a
metering roller and an application roller were positioned in
parallel at a pre-determined fixed distance from each other. Each
roller has approximately the same physical dimensions. The rollers
were held at the same elevation and their bottoms were submerged in
a liquid resin bath of the polymeric binder material contained in a
pan. The metering roller was held stationary while the applicator
roller rotated in a direction that would lift some of the liquid in
the resin bath towards the gap between the rollers. Only the amount
of liquid that will fit through this gap is carried to the upper
surface of the applicator roll, and any excess falls back into the
resin bath.
Concurrently, the support was carried towards the upper surface of
the applicator roll, with its direction of travel being opposite to
the direction the upper surface of the rotating applicator roll.
When the support was directly above the applicator roll, it was
pressed onto the upper surface of the applicator roller by means of
a backing roller. All of the liquid that was carried by the upper
surface of the applicator roller was then transferred to the
support. This technique was used to apply a precisely metered
amount of liquid resin to the surface of the silicone-coated
release paper.
The dip and squeeze technique was conducted to coat the fibrous web
with the diluted resin dispersion using the following steps: 1.
Spools of TWARON.RTM. yarn were unwound from a creel. 2. The yarns
were sent through a though a series of combs, which caused the
yarns to be evenly spaced and parallel to each other. At this
point, the individual yarns were closely positioned and parallel to
one another in a substantially parallel array. 3. The substantially
parallel array was then passed over a series of rotating idler
rollers that redirected the substantially parallel array down and
through the liquid resin bath. In this bath, each of the yarns were
completely submerged into the liquid for a length of time
sufficient to cause the liquid to penetrate each yarn bundle,
wetting the individual fibers or filaments within the yarn. 4. At
the end of this liquid resin bath, the wetted fibrous web was
pulled over a series of stationary (non-rotating) spreader bars.
The spreader bars spread out the individual yarns until they
abutted or overlapped with their neighbors. Before spreading, the
cross-sectional shape of each yarn bundle was approximately round.
After spreading, the cross-sectional shape of each yarn bundle was
approximately elliptical, tending towards a rectangle shape. An
ultimate spread would be for each fiber or filament to be next to
one another in a single fiber plane. 5. Once the wetted fibrous web
passed over the last spreader bar, it was again re-directed, this
time up and out of the liquid. This wetted fibrous web then was
wrapped around a large rotating idler roller. The fibrous web
carried with it an excess of the liquid. 6. In order to remove this
excess liquid from the fibrous web, another freely rotating idler
roller was positioned to ride on the surface of the large rotating
idler roller. These two idler rollers were parallel to each other
and the freely rotating idler roller was mounted in such a way that
it beared down on the large rotating idler roller in a radial
direction, effectively forming a nip. The wetted fibrous web was
carried through this nip and the force applied by the freely
rotating idler roller acted to squeeze off the excess liquid, which
ran back into the liquid resin bath.
At this point, the coated fibrous web and the coated
silicone-coated release paper are brought into contact with one
another on the "combining roller". The wetted (impregnated) fibrous
web is cast onto the wet side of the silicone-coated release paper
and passed over the combining roller such that the NUVA.RTM.
LB-coated aramid fiber web is pressed into the wet coating of
HYCAR.RTM. T122 that was carried on the surface of the
silicone-coated release paper. The coating of HYCAR.RTM. T122
appeared to penetrate or extrude through the saturated aramid fiber
web, without disrupting the good spread of the fiber web. The
assembly was then passed through an oven to dry off the water.
A series of squares were cut from this unidirectional tape ("UDT").
Two squares were then oriented fiber-side to fiber-side and one of
the squares was rotated so that the direction of its fibers was
perpendicular to the fiber direction of the first square. These
pairs of configured squares were then placed into a press, and
subjected to 240.degree. F. (115.56.degree. C.) and 100 PSI (689.5
kPa) for 15 minutes. The press was then cooled to room temperature
and the pressure was released. The squares were now bonded to one
another. The release paper was removed from both sides of this
composite, resulting in a single layer of a non-woven fabric. This
procedure was repeated to produce additional layers as needed for
ballistic testing.
Overall, a roll of UDT made using this hybrid coating technique was
of very good quality. The yarn spread was good, the amount of resin
added to the fibrous web was very consistent and the UDT was
anchored down to the silicone-coated release paper well enough to
allow further processing.
EXAMPLE 2 (COMPARATIVE)
Using the same machine setup as in Example 1, another UDT roll of
TWARON.RTM. 1000-denier, type 2000 aramid yarns was formed. In this
example, the dilute dispersion in the yarn impregnator was replaced
with de-ionized water and the amount of the HYCAR.RTM. T122 acrylic
resin that was coated onto the silicone-coated release paper was
increased by about 20%. The de-ionized water in the yarn
impregnator aided the aramid fiber in spreading. At the combining
roller, the wetted aramid fiber web was pressed into the wet
coating of HYCAR.RTM. T122 that was carried on the surface of the
silicone-coated release paper. As in Example 1, the coating of
HYCAR.RTM. T122 appeared to penetrate or extrude through the
saturated aramid fiber web without disrupting the good spread of
the fiber web. The increased amount of the HYCAR.RTM. T122 acrylic
dispersion that was coated onto the silicone-coated release paper
was meant to offset the missing weight added from the yarn
impregnator, normalizing the total amount of resinous matrix added
to the fibrous web so that a similar amount of total matrix
material was added to the fibrous webs in both Example 1 and
Example 2.
Overall, a roll of UDT made using this hybrid coating technique was
of very good quality. The yarn spread was good, the amount of resin
added to the fibrous web was very consistent and the UDT was
anchored down to the silicone-coated release paper well enough to
allow further processing.
Next, a series of squares were cut from this unidirectional tape
roll similar to Example 1 and were then further processed into
cross-plied, non-woven fabrics for subsequent evaluation.
Four shoot-packs were prepared from the non-woven fabrics of both
Example 1 and Example 2. Each shoot-pack consisted of 46 layers of
the 2-ply non-woven fabric. Each layer measured approximately 13''
by 13''. The stack of 46 layers was placed into a nylon fabric
carrier which was sewn closed. Each shoot-pack was then corner
stitched to help the integrity of the shoot-pack during further
handling and testing. The samples were numbered and weighed. The
weights and other details are summarized in Table 1 below.
TABLE-US-00001 TABLE 1 Total Areal Actual Resin Density Weight
EXAMPLE Sample ID Content Layers (lb/ft.sup.2) (LBS) 1 1A 13.8% 46
0.98 PSF 1.24 (4.79 kg/m.sup.2) (563 g) 1 1B 13.8% 46 0.98 PSF 1.27
(4.79 kg/m.sup.2) (576 g) 1 1C 13.8% 46 0.98 PSF 1.26 (4.79
kg/m.sup.2) (572 g) 1 1D 13.8% 46 0.98 PSF 1.25 (4.79 kg/m.sup.2)
(567 g) 2 2A 15.5% 46 1.02 PSF 1.30 (4.98 kg/m.sup.2) (590 g) 2 2B
15.5% 46 1.02 PSF 1.28 (4.98 kg/m.sup.2) (581 g) 2 2C 15.5% 46 1.02
PSF 1.27 (4.98 kg/m.sup.2) (576 g) 2 2D 15.5% 46 1.02 PSF 1.28
(4.98 kg/m.sup.2) (581 g)
These eight samples were subjected to salt water immersion testing.
In this testing, one half of the samples are shot dry with a series
of 16 grain RCC Fragments according to the MIL-STD-662E testing
method. The velocity of the projectiles was adjusted to achieve a
mixture of complete penetrations and partial penetrations of the
sample. The velocity of each shot was measured and a V.sub.50
((FPS) ft/second) for the sample was determined using accepted
statistical analysis tools. The balance of the samples were soaked
for 24 hours in a bath of a salt water solution (3.5% sea salt),
and allowed to drip-dry for 15 minutes before being subjected to
similar ballistic testing. The results are summarized in Table 2
below.
TABLE-US-00002 TABLE 2 Dry Wet Sample Weight Weight V.sub.50 AVG
Retention Example ID Exposure (LBS) (LBS) (FPS) (FPS) (Wet/Dry) 1
1A Dry 1.24 N/A 2038 2037 N/A (563 g) (621 mps) (620.9 mps) 1 1B
Dry 1.27 N/A 2035 N/A (576 g) (620 mps) 1 1C Wet 1.26 1.30 2005
2067 101.4% (572 g) (590 g) (611 mps) (630.0 mps) 1 1D Wet 1.25
1.29 2128 (567 g) (585 g) (649 mps) 2 2A Dry 1.30 N/A 2008 2022 N/A
(590 g) (612 mps) (616.3 mps) 2 2B Dry 1.28 N/A 2035 N/A (581 g)
(620 mps) 2 2C Wet 1.27 1.58 1882 1877 92.8% (576 g) (717 g) (574
mps) (572.1 mps) 2 2D Wet 1.28 1.67 1871 (581 g) (757 g) (570
mps)
The above data shows that the application of a thin coating of a
fluorocarbon-containing resin to the aramid fiber, and coating the
still wet fiber with a conventional matrix binder polymer, achieves
a substantial improvement of ballistic properties for a fabric that
has been submerged in salt water. In Example 1, the two dry samples
had an average V.sub.50 of 2037 ft/second (fps). The two samples
that were immersed in salt water for 24 hours and then drip-dried
for 15 minutes had an average V.sub.50 of 2067 fps. This indicates
that the construction and composition of Example 1 was resistant to
performance degradation from the salt water exposure.
In Comparative Example 2, the two dry samples had an average
V.sub.50 of 2022 fps. The two samples that were immersed in salt
water for 24 hours and then drip-dried for 15 minutes had an
average V.sub.50 of 1877 fps. This indicates that the construction
and composition of Example 2 experienced some performance
degradation from the salt water exposure.
Another important observation made during this testing was the
apparent effect of the fluorocarbon resin on the weight gain of the
samples that were subjected to the 24 hour salt water immersion.
Samples 2C and 2D, which were produced using only HYCAR.RTM. T122
acrylic dispersion as the binder, gained an average of 27% weight
after the 24 hour salt water immersion. Samples 1C and 1D, which
were produced by applying a thin coating of Clariant NUVA.RTM. LB
to the fibers before coating with the Noveon HYCAR.RTM. T122,
gained an average of approximately 3%. It is evident that some of
the NUVA.RTM. LB, which was applied directly to the surface of the
fiber, managed to migrate to the outer surface of the composite,
increasing its bulk water repellency. This was an unexpected
result, with the original intention of the NUVA.RTM.LB being used
specifically to protect the aramid fiber from degradation after
exposure to the salt water.
While the present invention has been particularly shown and
described with reference to preferred embodiments, it will be
readily appreciated by those of ordinary skill in the art that
various changes and modifications may be made without departing
from the spirit and scope of the invention. It is intended that the
claims be interpreted to cover the disclosed embodiment, those
alternatives which have been discussed above and all equivalents
thereto.
* * * * *